The invention concerns a blood lancet device for withdrawing blood for diagnostic purposes.
Lancets are used in diagnostic applications to withdraw a small amount of blood by pricking a part of the body (usually the finger or the ear-lobe). In the past, the puncturing procedure had been carried out by trained, specially educated personal either manually or using a simple apparatus. This method to obtain a blood sample is acceptable when blood investigations must only be carried out occasionally, since in this case the pain associated with the puncturing does not play a decisive role.
The requirements for blood withdrawal are substantially more stringent when regular monitoring of certain analytic values in the blood of a patient is necessary. This is particularly the case for diabetics whose blood sugar levels must be monitored frequently and regularly in order to keep these levels (which depend on food ingestion, physical activity and other factors) within certain limiting values through the administration of insulin injections. Such an intensive blood sugar therapy is of extreme importance to the health of the patient and requires at least four blood withdrawals per day. For example, the publication
xe2x80x9cThe Effect of Intensive Treatment of Diabetes on the Development and Progressing of Long-term Complications in Insulin-dependent Diabetes Mellitusxe2x80x9d, of the Diabetes Control and Complications Trial Research Group, New England Journal of Medicine, 1993, 977 to 986 reports that intensive therapy, involving at least four blood samples per day, can reduce the probability of retinopathy (which eventually leads to blinding of the patient) by 76%. This is also the case for other serious long term damage associated with diabetes mellitus.
Long-term intensive blood sugar therapy is only feasable by so-called xe2x80x9chome-monitoringxe2x80x9d carried out by the patient himself or by family members without the use of trained medical personal. The willingness and capability of the patient to obtain a blood sample by means of a lancet at least four times daily depends decisively on the properties of the blood withdrawal device. It must be so designed that the pain associated with generation of the wound necessary for blood withdrawal is as low as possible. The device must be as simple to operate as possible, since a large share of the patients are, due to their illness or advanced age, not capable of carrying out difficult manual operations in a precise fashion. In addition, low weight and a practical shape are important in order that the device can be easily carried along with the patient. In addition, the design should be as simple as possible, it should be durable, and inexpensive.
Blood withdrawal devices and associated lancets have been proposed having various structural configurations to satisfy these requirements. They are described, by way of example, in the following US patents:
April 1984 U.S. Pat. No. 4,442,836 Meinecke
August 1985 U.S. Pat. No. 4,535,769 Burns
September 1984 U.S. Pat. No. 4,469,110 Slama
March 1987 U.S. Pat. No. 4,653,513 Dombrowski
January 1990 U.S. Pat. No. 4,895,147 Bodicky
May 1990 U.S. Pat. No. 4,924,879 O""Brien
June 1994 U.S. Pat. No. 5,318,584 Lange
September 1996 U.S. Pat. No. 5,554,166 Lange.
Although these known designs provide substantial improvements in blood withdrawal for diagnostic purposes, they cannot completely satisfy all of the previously mentioned requirements. In particular, those devices which produce the wound with very low pain levels have disadvantages with regard to handling and/or shape and size of the device. Conversely, small and easily operated devices are associated with insufficiently low pain levels.
It is an object of the invention to create an improved blood withdrawal device which better satisfies the above mentioned requirements.
The purpose is achieved by a device for withdrawing blood for diagnostic applications, comprising an elongated housing on the front end of which an exit opening is provided for the tip of a lancet, a lancet holder which holds the lancet and which can be displaced within the housing in the direction of its main axis along a predetermined puncture path, a lancet guide for guiding the lancet holder along the predetermined puncture path and a lancet drive having a resilient drive spring which can be locked in a loaded state using a locking device and which converts the relaxing motion of the drive spring into a puncture motion after the locking device is released, wherein the lancet, held by the lancet holder, is moved with high velocity along the predetermined puncture path in the puncture direction until its tip exits out of the exit opening to produce a wound in a part of the body proximate the exit opening, and wherein a two-sided rotary/translatory transmission is provided in the housing, the entrance side of the rotary/translatory transmission converting the motion of a loading button, projecting out of the rear end of the housing and movable along a linear loading path into a rotational motion of a lancet drive rotor which rotates about a rotational axis running parallel to the axis of the device to load the lancet drive rotor by tensioning the drive spring, the exit side of the rotary disk converting, after release of the lancet drive, a rotational motion of the lancet drive rotor driven by the drive spring into the puncturing motion in the direction of the main axis.
The invention is also directed to a blood withdrawal kit comprising the following mutually adapted system components: a blood withdrawal device in accordance with the invention and lancets adapted to be held in the lancet holder of the device. Such blood withdrawal kits (which also can be referred to as blood withdrawal equipment) are initially sold in the form of a packaged unit containing both system components. Since the lancets can normally only be used once, they are also provided in separate packages for use by patients already having blood withdrawal devices.
The term xe2x80x9ctransmissionxe2x80x9d is to be understood in its general sense i.e. in terms of a kinematic device for coupling and converting motion. In the present case, the double sided rotary/translatory transmission transforms a translation motion of the loading button into a rotational motion of the lancet drive rotor and a rotational motion of the lancet drive rotor into a translational motion of the lancet holder and lancet. These transmission functions can in principle be realized by means of conventional mechanical engineering elements.
The invention has the following advantages:
It allows a very slim housing shape similar to a ballpoint pen (so-called pencil shape). The device is inconspicuous and easily carried by the user.
The device can be loaded and triggered using one hand only.
The device is operated in a simple and logical manner.
Very little pain is produced by the wound. This is partially due to the associated very low vibration level.
Despite these substantial improvements in function, the structure is simple and inexpensive.
Embodiments of the invention should take into consideration the fact that a low-pain puncture requires a very rapid and precise puncturing motion. To this end the drive spring should have a high spring constant. On the other hand, the loading button should be sufficiently easy to operate such that older and physically handicapped people can load the blood withdrawal device.
These problems are solved in a particularly effective fashion and the above mentioned advantages are realized to a particularly good degree using preferred embodiments having the features described hereafter and in the dependent claims. These features can be used in the blood withdrawal device of the invention either individually or in combination.
In accordance with a preferred embodiment, the lancet drive rotor comprises a slide surface running along a helical path and the loading button comprises a loading cam which slides via a contact surface on the slide surface of the helical path to convert a linear motion of the loading button into a rotational motion of the lancet drive rotor. The helical path is preferentially formed on a loading sleeve constituting a part of the drive rotor. The forward end of the loading sleeve facing the exit opening surrounds the lancet holder.
In accordance with an additional preferred embodiment of simple construction and having low vibration, a guiding cam is provided in proximity to the front end of the loading sleeve. It controls, in cooperation with a guide pin provided on the lancet holder, the puncturing motion and preferentially also the return motion of the lancet holder and the lancet contained therein. Control of the puncturing and return motions through cooperation between a guide pin and a guide cam is disclosed in the above mentioned US patents 5,318,584 and 5,554,106.